VoIP Shield: A transparent protection of deployed VoIP systems from SIP-based exploits

In this paper, we present a lightweight defense mechanism against VoIP attacks, called VoIP Shield, that can detect counterfeit or MITM modified messages as well as replay attacks without ever changing the underlying VoIP protocol. We then empirically tested our design in conjunction with deployed Vonage VoIP services against a large body of attacks including billing, call redirection, voice pharming, and complex MITM exploits. The results demonstrate that advanced VoIP protection is practical, lightweight, and can be deployed even in systems where software upgrades are impossible.